In:
Review of Scientific Instruments, AIP Publishing, Vol. 83, No. 10 ( 2012-10-01)
Abstract:
The quality of plasma produced in a magnetic confinement fusion device is influenced to a large extent by the neutral gas surrounding the plasma. The plasma is fueled by the ionization of neutrals, and charge exchange interactions between edge neutrals and plasma ions are a sink of energy and momentum. Here we describe a diagnostic capable of measuring the spatial distribution of neutral gas in a magnetically confined fusion plasma. A high intensity (5 MW/cm2), narrow bandwidth (0.1 cm−1) laser is injected into a hydrogen plasma to excite the Lyman β transition via the simultaneous absorption of two 205 nm photons. The absorption rate, determined by measurement of subsequent Balmer α emission, is proportional to the number of particles with a given velocity. Calibration is performed in situ by filling the chamber to a known pressure of neutral krypton and exciting a transition close in wavelength to that used in hydrogen. We present details of the calibration procedure, including a technique for identifying saturation broadening, measurements of the neutral density profile in a hydrogen helicon plasma, and discuss the application of the diagnostic to plasmas in the DIII-D tokamak.
Type of Medium:
Online Resource
ISSN:
0034-6748
,
1089-7623
Language:
English
Publisher:
AIP Publishing
Publication Date:
2012
detail.hit.zdb_id:
209865-9
detail.hit.zdb_id:
1472905-2
SSG:
11
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